Leonard: See? Now, that's the great thing. We're out as friends. This is not a date. Sex is off the table. So, let's go learn why hydroelectric power might not be the environmental bargain you think it is. Sorry. Spoiler alert.

Leonard: What would you be if you were attached to another object by an inclined plane, wrapped helically around an axis?
Sheldon: Screwed?
Leonard: There you go.

Sheldon: This song is never going to stop. Have you ever dealt with something so relentlessly irritating?
Leonard: That's a trick question, right?

Leonard: My point is, while you're spending all this time on your own, building computers or practicing your cello, what you're really doing is becoming interesting. When people finally do notice you, they're gonna find someone a lot cooler than they thought. And for those of you that were popular in high school, it's over, sorry. Thank you. Congratulations.

Amy: If you're keeping him, I've got a cage you can borrow. One of the test monkeys slipped on a banana peel and broke his neck. It was both tragic and hysterical.

Sheldon: Get back here, you stupid bird, so I can love you.

Penny: Really? On top of everything, you're afraid of birds?
Sheldon: Its called ornithophobia and someday it will be recognized as a true disability, and the landlord will be required by law to put a giant net over the building. Which is unfortunate because I have a fear of nets.